Added items to CHANGELOG
(#439)
Put CHANGELOG in order by issue number.
Merge branch 'master' into #439

Conflicts:
	CHANGELOG.md
typos
(#439)
Merge branch '#439' of https://github.com/GalSim-developers/GalSim into #439
Fix the scons build for bug in scons <= 2.0.
Correct oversight error in test_shear.py
InputCatalog items are safe to reuse if component items are safe.  (e.g. if index is a constant, rather than a Sequence)
(#449)
Improve optimization flags we use for g++
(#449)
Use explicit SSE code for time-critical part of KTable.interpolate
(#449)
Store invdk, invN, etc. at class level so don't have to recalculate each time.
(#449)
some preparations for tagging v0.5
(#439)
Revert "some preparations for tagging v0.5"

This reverts commit 1d50549ef4d42f404ee6f9fef17062636eb811cb.
some preparations for tagging v0.5
(#439)
changelog, history updates post-tag of v0.5
merged in master, updated to v0.5.1 with changes in this branch
(#439)
Put back a CHANGELOG item Rachel accidentally removed
(#439)
Merge branch '#439' into #449
Don't add components to an Add object if flux=0
(#449)
more micro-optimizations in interpolate
(#449)